The present invention relates to a developing device which is employed in a wet type electrophotographic apparatus and the like, more particularly, to a developing device having a development electrode cleaning unit for cleaning the development electrode which is provided with the developing device so that an improved image is obtained through a developing operation executed by the developing device.
Conventionally in this type of developing device a development electrode is employed to generate an electric field to propel toner particles included in the developing solution. Without such an electrode it would take a relatively long time to develop an image on a surface of photo-conductive material on which a latent image has been formed simply by dipping the photo-conductive material in the developing solution. Further, if the development electrode is not employed, the image obtained through the developing operation is strongly affected by the so-called "Edge" effect.
Thus, the conventional developing device is provided with at least one development electrode, for generating an electric field to propel the toner particles, so as to shorten the time required for obtaining a sufficiently clear image as well as to remove the affect of the Edge effect. The developing device which is provided with a development electrode supplies the developing solution to the development electrode so as to cause the developing solution to contact with the photoconductive material.
However, since residual toner is gradually stuck to the surface of the development electrode with each developing operation, the intensity of the electric field generated by the development electrode is weakened. Thus, it becomes necessary to clean the surface of the development electrode.
The following two methods for cleaning the surface of the development electrode have been widely employed.
(1) Dismounting the development electrode from the developing device and wiping the residual toner stuck to the surface of the development electrode with a piece of cloth or sheet, or
(2) Applying a DC(Direct Current) voltage which is the same polarity as that of the toner particles to the development electrode, and simultaneously, vibrating the development electrode with an ultra-sonic wave for removing the residual toner, as disclosed in Japanese Patent Provisional Publication SHO No. 50-1745.
However, in the above method (1), it becomes necessary to dismount the development electrode from the developing device in order to clean it. Further, the cleaning operation is complicated and takes much time.
On the other hand, in the above method (2), the circuit required for oscillating the ultra-sonic wave is complicated and the total cost of the developing device increases.